Drivers of trucks and the like are typically required by law to ensure that loads they carry are properly restrained. Proper restraint of loads is required to ensure the safety of other road users.
One technique used for restraining a palletted load on the bed of a truck is to utilise a length of webbing and a winch. One end of a length of chain or webbing is secured at one edge of the truck bed, is passed over the palletted load, and the free end is wound onto the winch. The winch includes a spindle which is driven by inserting one end of a bar into an aperture through the spindle and rotating the bar. A pawl on the winch cooperates with a series of teeth on the spindle to keep the winch in a tightened state.
The truck body obstructs rotation of the bar, thus the winch is tightened in a series of part rotations. The bar is rotated through a partial turn, is removed, and re-inserted into the spindle in its initial rotational position so that it can be turned again. The spindle continues to be turned a little at a time until the desired tension in the webbing is achieved.
The continual removal and re-insertion of the bar into the spindle is time consuming, particularly in the case of soft, compressible loads. Thus, it has been tried to provide a ratchet mechanism in the spindle. The bar is rotated to tighten the winch, and when its limit of rotation is reached it can be rotated back to its starting position without removing it from the aperture. The winch is kept tight by the existing pawl mechanism, and the ratchet mechanism allows the bar to rotate back to its starting position. However, to date these ratchet type mechanisms have been found to be very vulnerable to failure.